From: Jim (nhatquang@thiennam.org)
Date: Sat May 07 2005 - 13:53:45 GMT-3
Anthony,
To prevent some sorts of unforeseen trouble, I think it is better to
unconditionally set port connected to router to access mode by sw mode access
unless the task requires something else. Sometimes you will have trouble at
last minutes after DLSW+ section! What will happen to a dynamic port connected
to router when they discover BPDU packets from another end through a DLSW+
link?
Jim.
----- Original Message -----
From: Anthony Sequeira
To: Hotmail
Cc: Group Study
Sent: Saturday, May 07, 2005 7:43 PM
Subject: Re: Switchport mode access
Yes - you are right on here - the switchport mode access command
unconditionally sets the port to be an access port. This would prevent
you from trunking.
Here is a lab scenario I just set up - DSW1 and DSW2 are connected via
their Gi 0/9 ports - and they are trunking by default thanks to the
default mode of dynamic desirable. In fact - it is an ISL trunk that
they have formed automatically (sure wish they would negotiate 802.1q
instead!).
On DSW1 I issue the command switchport access vlan 20 - and really
nothing happens because trunking is still being negotiated. Here is
the verification:
DSW1#show int gi 0/9 switch
Name: Gi0/9
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: trunk
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: isl
Negotiation of Trunking: On
Access Mode VLAN: 20 (VLAN0020)
...
Now - if I try the switchport mode access command as well - things do
in fact change! As you can see - no more trunk - even though DSW2 is
trying very hard to still form one.
DSW1#show int gi 0/9 switch
Name: Gi0/9
Switchport: Enabled
Administrative Mode: static access
Operational Mode: static access
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: native
Negotiation of Trunking: Off
Access Mode VLAN: 20 (VLAN0020)
...
In the lab - to save time - I plan on just using the command
switchport access vlan XX unless the instructions force me to do
otherwise. This is because I do not need to worry about a switch being
on the other end of the connection and negotiating a trunk! In the lab
- it is going to be routers on the other end of the access ports for
sure.
HTH,
Anthony Sequeira
On 5/7/05, Hotmail <pauwen@hotmail.com> wrote:
> Hello group,
>
> the command 4switchport mode trunk4 is used to prevent a port from
reverting
> to access mode when trunk negotitaion fails. Does it work the other way
around
> as well, that is, a switchport configured in 4switchport mode access4 can
> never revert to being a trunk port ? The reason I am asking is that I
have
> seen configurations like this:
>
> interface FastEthernet0/1
> switchport access vlan 3
>
> and this:
>
> interface FastEthernet0/1
> switchport mode access
> switchport access vlan 3
>
> Is the difference that in the first configuration, the port could still
revert
> to being a trunk port, while in the second, it cannot ?
>
> Thanks for your help in advance.
>
> GP
>
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